I was thinking about getting the Tarmac wheels from fifteen52. They come in 17x8, 17x9, 18x8.5, 18x9.5, and 19's but thats obviously too big. I know the easy choice would be the 17x8, but I would like an 18x8.5. So my question is can I run these on 225/40 w/o rub? Fifteen52 does offer custom offset.

I found that site while I was sizing wheels/tires for my Forester and like it much better than anything else I've found simply because it provides a visual reference.

Based on what I figured as a stock offset using the stock tire size of 205/55/16, I played around with the offset.

To keep the wheel from moving any further in than stock, you'll want an offset of 33mm. The wheel will stick out 38mm farther than it used to. Play around with different offsets to see how you like the fitment.

Either way, sticking that far out may pose problems rubbing on the outer fender, depending on your suspension setup. You may be able to go farther in, I'll have to check clearance on factory wheels when I get out to the garage this week.

heavywoody wrote:Come to think of it, they might be 48... I can't remember.

Either way, sticking that far out may pose problems rubbing on the outer fender, depending on your suspension setup. You may be able to go farther in, I'll have to check clearance on factory wheels when I get out to the garage this week.

A quick search says the same thing; I'll double check tonight if I have time on my GTU wheels. I'll also check how much clearance is available to the spring perch, which will help you determine how much offset you can get away with.

heavywoody wrote:A quick search says the same thing; I'll double check tonight if I have time on my GTU wheels. I'll also check how much clearance is available to the spring perch, which will help you determine how much offset you can get away with.

Thanks I really appreciate it! I might go with the 17x8 if I can fit the 18's.

If you have a stock tire/wheel on there now and know the current width then just measure between the tire and the spring perch... now if you keep the same diameter tire overall, then as it sits you would need to have at minimum a 1" clearance between the tire and perch since going to a 18x9 will increase the width by 1" inboard and outboard. That is of course if you keep the 42mm offset. If you go a lower number you will push the tire out and I can tell you that on a 16x7" rim with 35mm offset the tire was near flush with the front fender lip, so regardless of inner clearance that would tell me that a stock tire face is 7mm or approximately 1/4" off the face of the fender flare. This doesn't leave you with much room, outboard at least, to add over 2" to the overall rim width and not have the tire stick out beyond the lip of the fender... SO hopefully there is ample distance between the tire and spring perch which would accommodate a higher offset but I don't think that exists either.